Combustors are commonly used in industrial and commercial operations to ignite fuel to produce combustion gases having a high temperature and pressure. For example, industrial gas turbines typically include one or more combustors to generate power or thrust. A typical commercial gas turbine used to generate electrical power includes an axial compressor at the front, one or more combustors circumferentially arranged around the middle, and a turbine at the rear. Ambient air may be supplied to the compressor, and rotating blades and stationary vanes in the compressor progressively impart kinetic energy to the working fluid (air) to produce a compressed working fluid at a highly energized state. The compressed working fluid exits the compressor and flows through one or more nozzles in each combustor where the compressed working fluid mixes with fuel and ignites in a combustion chamber to generate combustion gases having a high temperature and pressure. The combustion gases flow to the turbine to produce work. For example, expansion of the combustion gases in the turbine may rotate a shaft connected to a generator to produce electricity.
It is well-known that the thermodynamic efficiency of the gas turbine generally increases with higher combustion gas temperatures. However, higher combustion gas temperatures may also increase the production of undesirable emissions, reduce the design margins for flame flash back and/or flame holding, and/or expose various combustor components to excessive temperatures. As a result, a variety of techniques exist to allow higher combustion gas temperatures while minimizing undesirable exhaust emissions, flash back, flame holding, and excessive temperatures. Many of these techniques seek to enhance uniform mixing of the fuel and compressed working fluid prior to combustion to reduce or prevent localized hot spots in the combustion chamber associated with the undesirable emissions, flash back, and/or flame holding.
Additional techniques seek to increase cooling to the combustor components to prevent excessive temperatures from damaging the combustor components. Specifically, a portion of the working fluid may be directed across the outside of the combustor components exposed to the higher temperature combustion gases to provide impingement, convective, and/or conductive cooling to the combustor components. Axial injection of the working fluid across the outside of the combustor components reduces the pressure loss of the working fluid across the combustor, which in turn increases the combustion gas flow and overall efficiency of the gas turbine. However, the structures used to axially inject the working fluid across the outside of the combustor components have increased the complexity, manufacturing costs, and/or maintenance costs associated with the combustor. Therefore, an improved combustor and method for supplying axial flow across the outside of the combustor components would be useful.